Recently Cogan (1981) proposed a dual-channel model of binocular functioning. Binocularly matched contours (i.e., corresponding contours that are similar in sharpness, contrast, and other attributes of contour strength) are processed in a fused channel, while unmatched contours are routed to a different, interocular branch of the system. The nt output of the system is produced either by the fused channel, the interocular channel, or through interaction between the fused channel and one monocular channel. The model is based on the monocular and binocular detection of luminance increments by normal subjects. Thresholds are significantly altered by the presence of vertically or horizontally oriented gratings presented monocularly to either eye, or binocularly. Monocular sensitivity was best in the uniform field. In the presence of contours, sensitivity was better in the perceptually dominant eye. In fusion, as in rivalry, there was a net decrease in sensitivity but the probable mechanisms are different: during fusion, background luminances in the area delimited by fused contours can be binocularly summed; then, increments presented monocularly are proportionally attenuated, provided the monocular stimuli are not strong enough to disrupt fusion; during rivalry, the probability of seeing is decreased due to interocular alternation. We intend to examine increment thresholds in a population of subjects where binocular functioning may have been disrupted by anisometrophia, astigmatism and amblyopia. The main question is: Does contour strength affect binocular interactions in the ways predicted by our model? Increment thresholds will be measured, along four principal meridians, monocularly and binocularly, in a uniform field and then in the presence of contours. Threshold elevation in the contoured field will give an estimate of contour strength. The amount of binocular improvement (given by the ratio of binocular over monocular performance) will yield estimates of monocular dominance, binocular fusion, and the hypothetized interaction between the fused channel and the stronger monocular channel.